The act of swimming freestyle requires a combination of skills involving strength, aerobic fitness, flexibility, proprioception and positioning that enable the human body to move efficiently through the water. There are three groups of physical laws that govern all of the techniques used in the act of swimming. They are laws of drag (forces that slow us), motion (propulsion or forces that speed us up) and inertia. Swimming efficiently requires the observance of these laws with respect to minimizing frontal drag, maximizing propulsive forces and maintaining body speed as close to a constant as possible.
With respect to drag forces acting on the swimmer doing freestyle, the sport is somewhat unique in that the very act of the propulsive pulling motion of the arms, as they move through the pull cycle, change the shape of the human body drastically and thus also drastically change the frontal drag forces acting on the body. In addition, since the propulsion is occurring in liquid, in order to maximize the propulsive force of the arm/hand combination, a counter force is required by rotation of the body and a kick that increase the efficiency that is generated with each arm pull. Finally, in order to minimize frontal drag, the body must be kept in alignment from head to toe, while the rotation is occurring.
The amount of frontal drag that is caused by the underwater arm/hand pulling motion is also very different, depending on the position of the arm, forearm and hand, resulting from the articulation of the shoulder, elbow and wrist during this time. The least amount of frontal drag occurs as a result of keeping the upper arm as close as possible to alignment with the line of motion of the body during the early part of the underwater pull. This position, which is called early vertical forearm (EVF), is attained through internal rotation and extension of the shoulder joint during the body rotation. Later in the underwater pull, frontal drag is also reduced through keeping the elbow closer to the surface and sweeping the upper arm more to the side, rather than directly below the body. This described arm motion, although required to reduce frontal drag, is not the position of mechanically greatest strength of the arm throughout the underwater pull. However, based on the observation of some of the world's fastest swimmers, who appear to have a common use of this described motion under water, it appears that the reduction of frontal drag force is more important than maximizing propulsive force.
Acquiring this described pulling motion for swimmers, which for most is neither obvious nor intuitive, requires practice, flexibility and strength development. Being able to rotate the body while simultaneously achieving this pulling motion is also not obvious nor intuitive and requires practice, strength and flexibility. Keeping the body in alignment from head to toe, while achieving this underwater arm motion, also requires strength and practice.
One can acquire these skills in a swimming pool during the course of swimming practice, yet there is still an unmet need to create a swim bench that specifically addresses the need to develop these specific skills on land that will increase freestyle efficiency and speed.